Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B1/00—Electrolytic production of inorganic compounds or non-metals
  • C25B1/01—Products
  • C25B1/21—Manganese oxides
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
  • C01G45/00—Compounds of manganese
  • C01G45/02—Oxides
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
  • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2002/00—Crystal-structural characteristics
  • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
  • C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/10—Solid density
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/12—Surface area
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/14—Pore volume
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/40—Electric properties
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/80—Compositional purity
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/80—Compositional purity
  • C01P2006/82—Compositional purity water content
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/10—Energy storage using batteries

Definitions

• the present invention relates to electrolytic manganese dioxide for use as the cathode in batteries and methods of producing the electrolytic manganese dioxide. More particularly, the present invention provides electrolytic manganese dioxide which when utilized in batteries imparts higher discharge capacity at high discharge rates thereto.
• Electrolytic manganese dioxide referred to in the industry as EMD, is widely used as the cathode material in batteries. EMD was first utilized in zinc-carbon cells (Leclanche cells) , and later in alkaline cells.
• EMD is used in alkaline batteries to achieve high voltages, low polarization and high discharge capacities.
• the discharge capacity of alkaline batteries is dependent upon the quality of the EMD utilized.
• the mixture forming the cathode in alkaline batteries is about 82% EMD and is generally formed into an annular cathode by impact extrusion in the container or by the compression molding of pellets which are recompacted against the container. In both of these processes, the properties of the EMD must be very consistent to allow the battery manufacturer to consistently produce high quality batteries.
• Alkaline batteries have a higher capacity per unit volume than other zinc-manganese dioxide batteries, and are particularly capable of high discharge capacity, i.e., long life, at high discharge rates.
• the present invention provides improved high quality EMD for use as cathode material in batteries of high discharge capacity at high discharge rates and methods of producing such EMD by electro-deposition in an electrolytic cell.
• the electrolytic cell includes cathodic and anodic electrodes disposed therein through which an electric current is passed.
• a heated aqueous electrolyte solution comprising sulfuric acid and manganese sulfate is maintained in the electrolytic cell.
• the solution is of high purity and includes manganese sulfate therein in an amount whereby manganese is present in the range of from about 5 to about 50 grams of manganese per liter of solution.
• an electric current is applied to the cathodic and anodic electrodes and the electrolyte solution whereby the anodic electrode current density is in the range of from about 2.5 to about 6 amperes per square foot, and the high discharge capacity EMD produced is deposited on the anode.
• the temperature of the electrolyte solution in the electrolytic cell is carefully maintained in the range of from about 95°C to about 98°C.
• the sulfuric acid concentration in the electrolyte solution is maintained in an amount in the range of from about 20 to about 50 grams of sulfuric acid per liter of solution.
• the cathode utilized in the electrolytic cell is preferably comprised of copper, graphite or steel, as determined by cost.
• the anode is preferably comprised of titanium to provide minimum weight and volume, maximum strength, minimum weight loss, and adequate corrosion resistance. It is, therefore, a general object of the present invention to provide improved electrolytic manganese dioxide having higher discharge capacity at high discharge rates and methods of producing the same.
• FIGURE 1 is a plot of relative discharge energy in AA cells vs. the EMD deposition current density at 95°C,
• FIGURE 2 is a topographical representation of the relative energy in AA cells vs. the H 2 S0 4 and Mn 2+ concentrations as obtained from multiple regression of the experimental results (Table II) within the current density range of 2.5-6.0 A/ft 2 .
• FIGURE 3 is a scatter plot of the experimental relative discharge energies in AA cells vs. the BET surface areas of all the EMD samples in Table II.
• the open circle represents the reference Sample No. 41 in this and subsequent figures.
• FIGURE 4 is a scatter plot of the experimental relative discharge energies in AA cells vs. the compressed densities of the EMD samples.
• FIGURE 5 is a scatter plot of the experimental relative discharge energies in AA cells vs. the initial open circuit voltages of the EMD samples.
• FIGURE 6 is a scatter plot of the experimental relative discharge energies in AA cells vs. the intrinsic discharge capacities of the EMD samples.
• FIGURE 7 is a scatter plot of the experimental relative discharge energies in AA cells vs. the Q-ratio of the EMD samples.
• FIGURE 8 is a scatter plot of the experimental relative discharge energies in AA cells vs. the structural water content of the EMD samples.
• FIGURE 9 is a scatter plot of the experimental relative discharge energies in AA cells vs. the Mn0 2 content of the EMD samples.
• FIGURE 10 is an XRD scan of Sample No. 16, deposited under the conditions of the invention, i.e., 3.4 A/ft 2 , 96°C, 29 g/1 H 2 S0 4 and 9 g/1 Mn 2+ .
• FIGURE 11 is an XRD scan of Sample No. 4, deposited at 3.4 A/ft 2 , 96°C, 12 g/1 H 2 S0 4 and 9 g/1 Mn 2+ .
• Electrolytic manganese dioxide is produced by subjecting an aqueous electrolyte solution comprised of sulfuric acid and manganese sulfate to electrolysis in an electrolytic cell having cathodic and anodic electrodes disposed therein.
• the electrolysis process causes oxidation of the manganese sulfate at the anodic electrode and the deposition of a coating of the desired manganese dioxide product on the anode.
• the coating has built up to a desired thickness, the anode is removed from the electrolytic cell and the coating is removed therefrom.
• the present invention is based on the discovery that improved EMD for use as cathode material in batteries having an unexpected high capacity at high discharge rates, i.e., rates of from 1 to 3 watts in AA-cells, can be produced when a low anodic current density is utilized in combination with a low concentration of manganese sulfate in the electrolyte solution.
• the methods of the present invention for producing very high discharge capacity EMD by electrolysis in an electrolytic cell are basically comprised of the steps of maintaining a heated aqueous electrolyte solution comprising sulfuric acid and manganese sulfate in the electrolytic cell, the solution having manganese sulfate therein in an amount whereby manganese is present in the range of from about 5 to about 50 grams of manganese per liter of solution, and applying electric current to the electrodes whereby the anodic electrode current density is in the range of from about 2.5 to about 6 amperes per square foot and the high discharge capacity EMD produced is deposited on the anodic electrode.
• the aqueous electrolyte solution is maintained in the electrolytic cell at a temperature in the range of from about 95°C to about 98°C. Also, the concentration of sulfuric acid in the aqueous electrolyte solution is maintained in the range of from about 20 to about 60 grams of sulfuric acid per liter of solution.
• the anodic electrode utilized -loin the electrolysis process is preferably comprised of titanium as described in the above mentioned U.S. Patent No. 4,606,804, and the cathodic electrode is preferably comprised of copper as described in the above mentioned U.S. Patent No. 4,477,320.
• More preferred electrolysis conditions for carrying out the methods of this invention include maintaining the manganese sulfate in the aqueous electrolyte solution in an amount whereby manganese is present in the range of from about 5 to about 20 grams of manganese per liter of solution, applying electric current to the electrodes whereby the anodic electrode current density is in the range of from about 2.5 to about 3.5 amperes per square foot, maintaining the electrolytic solution at a temperature in the range of from about 95°C to about 98°C and maintaining the sulfuric acid concentration in the electrolyte solution in an amount in the range of from about 25 to about 40 grams of sulfuric acid per liter of solution.
• the concentration of the sulfuric acid in the electrolytic solution is maintained at a level greater than or equal to two times the concentration of manganese therein.
• the properties of the high discharge capacity EMD produced in accordance with the methods of this invention are considerably better than the properties of high discharge capacity EMD produced using prior art methods.
• the higher 1-watt discharge capacity and energy translate into longer running times in high rate applications, while the higher intrinsic discharge capacity ensures a greater capacity/running time at lower-rate applications.
• the greater initial open circuit voltage is valued by battery makers (and is part of the reason for the greater capacities) .
• the compressed density of the EMD is higher, which is very important from the standpoint of its use in batteries, i.e., more EMD can be placed in each cell.
• a preferred method of this invention for producing EMD having a high discharge capacity at high discharge rates by electrolysis in an electrolytic cell having cathodic and anodic electrodes disposed therein is comprised of the steps of maintaining a heated aqueous electrolyte solution comprising sulfuric acid and manganese sulfate in said electrolytic cell, the solution having manganese sulfate therein in an amount whereby manganese ion is present in the range of from about 5 to about 50 grams of manganese ion per liter of solution; and applying electric current to the electrodes whereby the anodic electrode current density is in the range of from about 2.5 to about 6 amperes per square foot and the high discharge capacity electrolytic manganese dioxide produced is deposited on the anodic electrode.
• a more preferred method of the present invention comprises the steps of maintaining an aqueous solution comprised of sulfuric acid and manganese sulfate in the electrolytic cell at a temperature in the range of from about 95°C to about 98°C, the solution having sulfuric acid therein in an amount in the range of from about 20 to about 60 grams of sulfuric acid per liter of solution and having manganese sulfate therein in an amount whereby manganese ion is present in the range of from about 5 to about 50 grams of manganese ion per liter of solution; and applying electric current to the electrodes whereby the anodic electrode current density is in the range of from about 2.5 to about 4.5 amperes per square foot and the high discharge capacity electrolytic manganese dioxide produced is deposited on the anodic electrode.
• the most preferred method of the present invention for producing EMD having a high discharge capacity at high discharge rates by electrolysis in an electrolytic cell containing cathodic and anodic electrodes comprises the steps of maintaining an aqueous solution comprised of sulfuric acid and manganese sulfate in the electrolytic cell at a temperature in the range of from about 95°C to about 98°C, the electrolyte solution having sulfuric acid therein in an amount in the range of from about 25 to about 40 grams of sulfuric acid per liter of solution, having manganese sulfate therein in an amount whereby manganese ion is present in the range of from about 5 to about 20 grams of manganese ion per liter of solution, the amount of sulfuric acid in the electrolyte solution being greater than or equal to two times the amount of manganese ion therein; and applying electric current to the electrodes whereby the anodic electrode current density is in the range of from about 2.5 to about 3.5 amperes per square foot and the high discharge capacity EMD produced
• EMD was deposited in bench cells that contained a titanium anode, two copper cathodes, and an aqueous electrolyte of high purity manganese sulfate (MnS0 4 ) and sulfuric acid (H 2 S0 4 ) .
• the cell consisted of a 4-liter battery jar, which contained the vertically suspended electrodes.
• the anode was a corrugated sheet of titanium 25 cm x 9.2 cm, and each of the two opposing cathodes consisted of two copper plates, 25 cm x 2 cm. Deposition for each test was conducted continuously for several weeks, the electrode reactions being Mn 2+ + 2H 2 0 ⁇ Mn0 2 (EMD) + 4H + + 2e (anode)
• the electrolyte concentration was monitored daily, and stayed within 1 g/1 of the target Mn 2+ and acid concentrations. Temperature in the cell was maintained by means of an immersion heater coupled with a thermoregulator. A thin layer of paraffin was maintained on top of the electrolyte to prevent evaporation. Current was supplied to the electrodes by means of a constant current power supply. Deposition cycles were generally three weeks. However, for many of the higher current density tests, the time was two weeks or less; also, for several very low current density tests, the deposition time was longer than three weeks. There is no indication that product quality varied with deposition time between 2 and 3 weeks. Thus, it was assumed that properties of the product depend only on the deposition parameters coupled with random imprecision.
• each anode was soaked in hot water to remove the paraffin, and then the deposit was removed from the titanium anode, crushed, ground, screened, blended and neutralized with a NaOH solution to pH 7.
• the final product had the following particle size distribution: 9% -100/+200 mesh, 25% -200/+325 mesh and 66% -325 mesh.
• More than 50 laboratory EMD samples were deposited over a wide range of deposition parameters, i.e., current density (i) , temperature (T) , sulfuric acid concentration ([H 2 S0 4 ]) and Mn 2+ -ion concentration ([Mn 2+ ]). After the trend of battery performance vs.
• the newly constructed AA cells were allowed to rest (equilibrate) for two to three days, and then were connected to a computerized Maccor battery test system and discharged at a rate of 1 watt.
• the discharge capacities and energies were determined at a cutoff voltage of 0.90V.
• Cells were made and discharged in weekly batches, with five cells per EMD sample and five EMD samples per week. Since many weeks were required to test all the EMD's, one sample was used as an internal standard and tested weekly along with the test samples for that week.
• the mean discharge energy (as well as the closely related discharge capacity) for the standard fluctuated somewhat from week to week, but averaged 0.675 Wh.
• the mean result for all cells of each test sample was divided by the mean result for the standard that was discharged in the same batch.
• Half-cell Tests Some of the samples were discharged in flooded half-cells. In “half-cell tests" the EMD is discharged and its potential is measured with respect to a fixed reference electrode. Thus, all the potential change is associated with the EMD discharge, as opposed to the full-cell (i.e., AA-cell) tests, in which the voltage change is shared by both the EMD cathode and zinc anode. Flooded half-cell tests are not influenced by the balance between anode, cathode and electrolyte. Accordingly, these tests were conducted to complement the AA-cell tests.
• the cathode having a diameter of 1.4 cm, contained a constant weight of EMD in each case, i.e., 0.727 g, and was approximately 1.9 mm thick.
• This electrode was suspended in a laboratory cell flooded with 9M KOH and discharged against an anode while its potential was measured against a zinc reference electrode. Discharge current was 100 mA/g-EMD and was supplied by a computerized battery test unit.
• EMD Samples The following physical, chemical and electrochemical properties of each EMD sample were determined: BET surface area, pore volume, pore-size distribution, compressed density, open-circuit voltage in 9M KOH solution, and intrinsic discharge capacity. Additionally, many of the samples were X-rayed using the powder diffractometer method, and some were also analyzed for percent Mn, Mn0 2 and + 110°C water (structural water) . Method descriptions and/or references are given below.
• Compressed Density A cathode mix consisting of 83% dried EMD, 11% KS-44 graphite (Lonza) and 6% 7.2M KOH was compacted into a cylindrical pellet between punches in a one-inch-diameter die. After compaction at 10,000 lb. force, the thickness of the pellet center was measured with a micrometer and the density of the pellet was calculated. The test was conducted in triplicate on each sample, and the results averaged.
• the cell was discharged at a constant current of 20 mA per gram of EMD.
• the intrinsic discharge capacity (in mAh/g-EMD) was determined as the capacity to a cutoff voltage of 1.000V.
• Three cells were assembled from each sample as well as from an EMD sample used as an internal standard with each batch of cells. Therefore, all IOCV's and intrinsic capacities are means of the triplicate tests and are referenced to the internal standard tested at the same time. The method is detailed in the following reference: S.F. Burkhardt, in Handbook of Mangarese Dioxides, Battery Grade , ed. by D. Glover, B. Schur-im, Jr., and A.
• Percent Structural Water or +110°C Water The samples were first dried overnight at 110°C. Then the water driven from the sample at 750°C was determined by means of a Karl Fischer titrator. Each sample was analyzed in triplicate, the individual determinations being conducted on different days.
• Percent MnO-, and Mn The Mn0 2 was determined trimetrically using FeS0 4 . First, an EMD sample is dissolved in an excess of standard acidic FeS0 4 solution to form Mn 2+ ions. Then, the excess Fe 2+ ions are back-titrated with standard permanganate (KMn0 4 ) solution. This method assumes that all oxidative power of the EMD is due to Mn(IV) or Mn0 2 . Total Mn was determined by first dissolving EMD with a Fe 2+ ion solution and then titrating the resultant Mn 2+ ions in neutral pyrophosphate solution with standard permanganate solution.
• Mn 2+ ions are titrated exactly to Mn 3+ ions.
• Each sample was analyzed in triplicate, the individual determinations being conducted on different days.
• Test Results Table II lists the EMD samples (first column) along with the deposition parameters (2 nd through 5 th columns) , relative AA-cell 1-watt discharge energies (6 th column) , and the physical, electrochemical and chemical properties of each (the remaining columns) .
• the table is arranged in order of increasing BET surface area of the EMD (top-to-bottom) .
• the sample used as the comparison standard in AA-cell tests was No. 41.
• i current density
• T temperature
• [H 2 S0 4 ] concentration of sulfuric acid
• [Mn 2+ ]concentration of Mn 2+ ions
• the materials described in the examples of the invention were as good as or better than any other materials tested.
• FIG. 2 shows the results of Eq. 1 in topographical form for fixed i and T, and variable [H 2 S0 4 ] and [Mn + ] . Lines are drawn for equal energy intervals of 3% between 91 and 112%. The best energies are observed near 30 g/1 H 2 S0 4 and 5 g/1 Mn 2+ . The energy then decreases as either [H 2 S0 4 ] or [Mn 2+ ] is increased. The energy then increases slightly again at [H 2 SO 4 ]>60-65 g/1.
• H 2 S0 4 concentrations are not desired, because they foster passivation of the bare titanium anodes, which raises the cell voltage during deposition and can cause cell shutdown.
• a significant finding is that the discharge energy is defined by not only the acid and Mn 2+ concentrations but also the ratio [H 2 S0 4 ] / [Mn 2+ ] , as evidenced from the shapes of the contour lines.
• Example 2 shows that the inventive EMD has superior high-drain battery performance to and also different properties than EMD deposited at prior art conditions.
• "Prior art EMD's" were taken as all those in Table II for which the deposition current density was 5.8 or 6.0 A/ft 2 (18 in number) .
• the present invention we use all the samples in Table II that were deposited under the most preferred conditions as defined in Example 1, i.e., 2.5-3.5 A/ft 2 , 95-98°C, 25-40 g/1 H 2 S0 4 and 5-20 g/1 Mn 2+ . This includes Samples 5, 11-16, 20, 21, 23, 24 and 35 (12 in number) . The performances and properties of all the samples within each group were averaged to represent the group.
• inventive EMD's Comparison of the inventive EMD's and the prior art EMD's are shown in Table III below in terms of the mean performance features or properties and the standard deviations for the individual values about the means. Several entries in Table III are those shown in Table I.
• inventive EMD's are statistically different from the prior art EMD's in most respects. In several cases the difference in property directly relates to obvious superiority in application, i.e., the higher 1-watt discharge capacity and energy translate into longer running time in high-rate applications; the higher intrinsic discharge capacity ensures a greater capacity at lower-rate applications; the greater initial open circuit voltage is valued by battery makers (and is part of the reason for the greater capacities) ; and greater compressed density translates into more material being placed in each cell.
• the other differences largely verify and define differences in structure, and provide the means by which EMD discharge rates differ.
• the pores defined by the BET surface area, the pore volume and the pore volume distribution, are the dislocations and interstitial spaces between solid crystallites and aggregates of crystallites.
• the prior art EMD's have more such space than the inventive EMD's at all levels (sizes) of interstices. This excess space interferes with proton movement through the EMD during discharge, the latter proton movement being necessary to sustain the electrochemical discharge reaction, which is given by Eq. (2) .
• FIG. 3 shows the experimental AA-cell discharge energies vs. the BET surface areas for all the samples of Table I. Vertical lines are drawn to define a surface-area range within which practically all the excellent EMD's lie (excellent EMD's being arbitrarily defined as earlier, i.e., those yielding AA-cell energies equal to or greater than 108% of Sample 41) . All such EMD's were deposited according to the preferred method of the invention. It is observed that the range of excellence does not screen out all sub-excellent materials. Rather, this range is meant to indicate whether or not a material has a high probability of being sub-excellent, by virtue of its surface area lying outside the range of excellence. The range of excellence is approximately 21-29 m 2 /g.
• EMD's deposited at current densities less than the inventive method i.e., ⁇ 2 A/ft 2
• EMD's deposited from electrolyte with non-preferred acid and/or manganese concentrations i.e., ⁇ 2 A/ft 2
• EMD's deposited from electrolyte with non-preferred acid and/or manganese concentrations i.e., ⁇ 2 A/ft 2
• EMD's deposited from electrolyte with non-preferred acid and/or manganese concentrations i.e., ⁇ 2 A/ft 2
• EMD's deposited from electrolyte with non-preferred acid and/or manganese concentrations i.e., ⁇ 2 A/ft 2
• EMD's deposited from electrolyte with non-preferred acid and/or manganese concentrations i.e., ⁇ 2 A/ft 2
• FIG. 4 shows the experimental AA-cell discharge energies as a function the compressed density for all the samples of Table I.
• the range of excellence defined as in Example 3, includes compressed densities between approximately 3.09 and 3.21 g/cm 3 . Compressed densities below the range of excellence are dominated by the same EMD's that possess surface areas that are too high (FIG. 3) ; these were deposited by prior art of higher current densities and/or lower temperatures than preferred. Compressed densities greater than the range of excellence contain the same EMD's that were outside the range of excellence on the low-surface-area side, as detailed in Example 3.
• FIGS. 5 and 6 show the experimental AA-cell discharge energies as functions of the initial open circuit voltages (IOCV's) and intrinsic discharge capacities, respectively, for all the samples of Table I.
• the range of excellence starts at approximately 1.62 V (IOCV) or 250 mAh/g (intrinsic capacity) and is unbounded on the high end.
• the results indicate that samples have little chance of excellence at high drain if their IOCV or intrinsic discharge capacity is less than that of Sample 41 (open circle) .
• Example 6 The X-ray diffraction (XRD) spectrum for a typical, good EMD is shown in FIG. 10. All the peaks in this spectrum are characteristic of EMD's and have been indexed as representing the continuous crystallographic series between the 7 ⁇ Mn0 2 and e-Mn0 2 phases. All the members of this series are often collectively termed y-e Mn0 2 .
• the crystallography of such EMD's may be defined further in terms of the ⁇ -Mn0 2 /e-Mn0 2 character of the EMD, defined as the relative peak heights of the 22° and 37° peaks (after correction for background) . This ratio of peak heights, 22°/37°, termed the "Q-ratio" is shown in FIG. 7 vs.
• /3-Mn0 2 is a battery-inactive phase in rapid alkaline discharge.
• Other EMD's deposited from low-acid baths i.e., ⁇ 15 g/1 H 2 S0 4
• FIGS. 8 and 9 show experimental AA-cell discharge energies as a function of the chemical composition for 17 of the 61 test EMD's, the chemical composition being defined by the percentage of structural water (FIG. 8) and Mn0 2 (FIG. 9) .
• the range of excellence is approximately 3.17-3.38% structural H 2 0 and 91.5-92.1% Mn0 2 . Samples that are outside these ranges of excellence because of low structural water content or high Mn0 2 content were deposited either at very low current density or in a slurry cell.
• Samples with structural water contents greater than the range of excellence or Mn0 2 contents less than the range of excellence generally were deposited by prior art methods at high current densities (> 5.8 A/ft 2 ) , low temperatures ( ⁇ 95°C) , or at non-preferred acid and manganese concentrations.
• Example 8 Table IV below shows the average relative flooded half-cell discharge capacities for 19 of the EMD's described in Table II. Each capacity is the mean of three or more individual cell capacities. As with the AA-cell energies, the half-cell capacities of Table IV are compared to the mean capacity for Sample 41, which was discharged more than 30 times from several different cathode mixes. The absolute capacity for Sample 41 was 227 mAh/g. Also given in Table IV are the EMD surface areas and the relative rankings of the deposition conditions based on Example 1.

Landscapes

• Chemical & Material Sciences (AREA)
• Inorganic Chemistry (AREA)
• Organic Chemistry (AREA)
• Electrochemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Materials Engineering (AREA)
• Engineering & Computer Science (AREA)
• Metallurgy (AREA)
• General Chemical & Material Sciences (AREA)
• Battery Electrode And Active Subsutance (AREA)
• Inorganic Compounds Of Heavy Metals (AREA)
• Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
• Primary Cells (AREA)

Applications Claiming Priority (3)

Publications (3)

Family

ID=22809936

Family Applications (1)

Country Status (12)

Families Citing this family (25)

Family Cites Families (26)

• 1998
  • 1998-12-21 US US09/217,168 patent/US6214198B1/en not_active Expired - Lifetime
• 1999
  • 1999-12-16 TW TW088122117A patent/TW483949B/zh not_active IP Right Cessation
  • 1999-12-17 AR ARP990106548A patent/AR021909A1/es unknown
  • 1999-12-20 AU AU22006/00A patent/AU765967B2/en not_active Expired
  • 1999-12-20 ES ES99966482.4T patent/ES2532830T3/es not_active Expired - Lifetime
  • 1999-12-20 GE GE4437A patent/GEP20043412B/en unknown
  • 1999-12-20 EP EP99966482.4A patent/EP1144729B1/de not_active Expired - Lifetime
  • 1999-12-20 WO PCT/US1999/030386 patent/WO2000037714A1/en not_active Ceased
  • 1999-12-20 KR KR1020017007776A patent/KR100610596B1/ko not_active Expired - Lifetime
  • 1999-12-20 BR BR9917004-3A patent/BR9917004A/pt not_active Application Discontinuation
  • 1999-12-20 JP JP2000589762A patent/JP5066313B2/ja not_active Expired - Lifetime
• 2000
  • 2000-07-06 US US09/610,821 patent/US6638401B1/en not_active Expired - Fee Related
• 2001
  • 2001-05-07 ZA ZA200103667A patent/ZA200103667B/en unknown

Also Published As

Similar Documents

Legal Events